The energy level of the EL2 defect in GaAs

The free electron concentration in semi-insulating GaAs material is larger than the intrinsic concentration. This is due to the contribution of electr ons originating from EL2 defects. The magnitude of this contribution implie s that the energy level associated with this defect lies near 0.6 eV and no t at 0.75 eV, as commonly assumed. We examine the various values which have been determined for this energy level and underline the difference found b etween photoluminescence and electrical techniques. We finally use a techni que derived from deep level transient spectroscopy to get a direct measurem ent of this energy level. We obtain a value of 0.58 eV, which is consistent with all observations. (C) 1998 Elsevier Science Ltd. All rights reserved.